The present invention relates to an exhaust gas purifying apparatus for purifying the exhaust gas of automobiles by utilizing a corona discharge. More particularly, this invention relates to an exhaust gas purifying apparatus having a streamer corona generating portion capable of generating a stable streamer corona discharge for a long period.
Hitherto, there has been known Japanese Patent Laid-Open Publication No. 57-20510 as a technique of this type. According to the conventional technique, a known exhaust gas purifying apparatus is composed of a cylindrical-type dust collector, and a desired number of discharge wires mounted within the hollow portion of the cylindrical-type dust collector, the discharge wires being supplied with a high voltage, thereby eliminating micro-particles such as tar particles and graphite from an exhaust gas. Specifically, the micro-particles floating in the exhaust gas are attracted to the wall of the dust collector by utilizing the function of a strong electrostatic field generated between the cylindrical-type dust collector and the discharge wires, thereby eliminating the dust.
According to the conventional technique, however, there has been a possibility of danger in that the discharge wires are sometimes disconnected when a spark discharge is generated between the dust collector and the discharge wires. Furthermore, the attracting force required for eliminating an injurious gas such as NOx and COx from the exhaust gas, is weak and insufficient.
Apparatuses utilizing a corona discharge phenomenon have recently been considered as effective devices for activating and eliminating such injurious gas. However, an effective apparatus for maintaining a desirable value for the attracting force with respect to the dust in the exhaust gas by means of a general corona discharge phenomenon has not been achieved.
To this end, it was necessary in order to realize the technique for eliminating the injurious gas by using the corona discharge to generate a particular corona that is a streamer corona and to insure the increment of the streamer corona.
Furthermore, it was necessary in order to generate a stable streamer corona for a long period to eliminate the influence affecting the generation of the streamer corona due to an attachment of carbonaceous particles or the like.